Oct 17, 2007 1300 UTC Day 1 Convective Outlook
Updated: Wed Oct 17 12:38:18 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the southern and central plains and ozarks today through thursday morning....   Please read the latest public statement about this event.

Categorical Graphic
20071017 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20071017 1300 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20071017 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20071017 1300 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 171233
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0733 AM CDT WED OCT 17 2007
   
   VALID 171300Z - 181200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTN THROUGH TONIGHT OVER
   PARTS OF AR...CNTRL AND ERN OK...ERN KS AND SRN/CNTRL MO...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM E TX AND THE LWR MS VLY N
   INTO THE LWR MO AND MID MS VLYS...
   
   ...SYNOPSIS...
   
   ...POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE POSSIBLE THIS
   AFTERNOON AND TONIGHT...WITH A THREAT FOR A FEW STRONG AND/OR...
   LONG-TRACK TORNADOES...
   
   A DEEP CLOSED LOW WILL EVOLVE OVER THE CNTRL PLNS THIS PERIOD
   AS STRONG MID/HIGH-LVL IMPULSE NOW IN NM IS PROPELLED NEWD BY STRONG
   PACIFIC JET STREAK SWEEPING E/SE ACROSS THE GRT BASIN.  THE NM
   TROUGH SHOULD REACH CNTRL KS EARLY TONIGHT AND EASTERN IA BY 12Z
   THURSDAY WHILE THE PACIFIC JET STREAK CONTINUES E/SE TO THE SRN HI
   PLNS.
   
   AT LWR LVLS...LEE CYCLONE NOW IN SE CO EXPECTED TO DEEPEN AS IT
   TRACKS NE ACROSS KS TODAY AND REACHES NE NEB/NW IA EARLY THURSDAY. 
   SFC PATTERN WILL BE COMPLICATED BY OUTFLOW FROM ONGOING STORMS IN
   THE SRN PLNS AND LWR MS VLY...AND BY DISJOINTED NATURE OF DEVELOPING
   WARM FRONT THAT ATTM EXTENDS FROM THE RED RVR VLY REGION ESE INTO
   NRN LA.  LEE TROUGH/DRYLINE EXTENDING S FROM THE CO LOW SHOULD MOVE
   E INTO WRN OK AND NW TX BY MID TO LATE AFTN...AND LIKELY WILL ALSO
   SERVE AS A FOCUS FOR SVR TSTM DEVELOPMENT.
   
   BY 12Z THURSDAY...EXPECT THAT WARM FRONT WILL HAVE BECOME
   BETTER-DEFINED AND WILL HAVE MOVED NE INTO THE MID MS/LWR OH VLYS...
   WHILE DEVELOPING COLD FRONT ACCELERATES SE ACROSS THE PLNS.
   
   ...SRN/CNTRL PLNS INTO THE LWR/MID MS VLYS THROUGH TONIGHT...
   BEGINNING OF AN ACTIVE 2-3 DAY SVR WEATHER EPISODE IS UNFOLDING ATTM
   AS TSTMS INCREASE IN COVERAGE/INTENSITY OVER THE SRN AND CNTRL PLNS
   IN ZONE OF INCREASING WAA/MOISTURE INFLUX AHEAD OF POTENT NM UPR
   IMPULSE.  THE STORMS SHOULD CONTINUE TO INCREASE AND MOVE/DEVELOP
   NEWD THROUGH THE DAY AS SFC HEATING AND PERSISTENT MOISTURE RETURN
   FURTHER DESTABILIZE REGION.
   
   STRENGTHENING LOW AND DEEP-LYR WIND FIELDS ACROSS THE MDT AND SLGT
   RISK REGIONS WILL BE MORE THAN ADEQUATE FOR STRONG SUPERCELLS...
   WITH DEEP SHEAR EXPECTED TO BE AOA 50 KTS OVER A BROAD SWATH FROM
   CNTRL/E TX NE INTO THE MID AND LWR MS VLYS THROUGH THE PERIOD.
   WHILE RICHEST MARITIME AIR WILL REMAIN CONFINED TO REGION INVOF
   DISSIPATING FRONTAL ZONE OVER E TX/LA AND AR...SEASONABLY RICH
   MOISTURE /WITH DEWPOINTS WELL INTO THE 60S/ WILL SURGE N BEYOND THE
   STL AREA BY EARLY THURSDAY AS 40-50 KT SSWLY LLJ BROADENS IN WARM
   SECTOR OF DEEPENING SFC LOW.  THE STEEPEST MID LVL LAPSE
   RATES...MEANWHILE...WILL SWEEP ENE FROM THE TX/OK PANHANDLE REGION
   THIS MORNING TO THE LWR MO VLY BY EVENING...ALONG AND N OF UPR JET.
   
   GIVEN THE COMPLEXITIES POSED BY EXISTING CONVECTIVE CLUSTERS AND THE
   DISJOINTED/DIFFUSE NATURE OF SFC BOUNDARIES...IT IS DIFFICULT TO
   CONFIDENTLY IDENTIFY A HIGH RISK CORRIDOR WITHIN THE BROAD AREA
   OUTLINED BY THE MDT/SGT RISK FORECASTS.  PRESENT INDICATIONS
   ...HOWEVER...ARE THAT THE MOST SUBSTANTIAL SVR THREAT MAY DEVELOP
   THIS AFTN THROUGH EARLY TONIGHT FROM CNTRL/ERN OK NNE INTO SE
   KS...AS /1/ SFC HEATING.../2/ CONTINUED MOISTURE INFLOW...AND /3/
   STRENGTHENING CONVERGENCE ALONG RESIDUAL OUTFLOW BOUNDARIES AND/OR
   TROUGH/DRY LINE SEGMENTS CREATE ENVIRONMENT FAVORABLE FOR STORM
   INITIATION.  COMBINATION OF MODERATE INSTABILITY /1000-1250 J PER KG
   SBCAPE/ AND STRONG DEEP SHEAR SUGGESTS HIGH LIKELIHOOD FOR SUSTAINED
   SUPERCELLS.  GIVEN BREADTH OF DESTABILIZING WARM SECTOR AND EXPECTED
   DEGREE OF DIRECTIONAL SHEAR...THESE STORMS COULD YIELD STRONG AND/OR
   LONG-TRACK TORNADOES...IN ADDITION TO LARGE HAIL AND DAMAGING WIND. 
   THE SVR THREAT LIKELY WILL SPREAD INTO WRN/SRN MO AND NW AR EARLY
   TONIGHT...AND ERN MO/WRN IL EARLY THURSDAY...AS FORCING FOR ASCENT
   IS MAXIMIZED AHEAD EJECTING UPR TROUGH.
   
   FARTHER S...TSTMS EXPECTED TO BECOME INCREASINGLY NUMEROUS TODAY
   INVOF DIFFUSE WARM FRONT FROM FAR ERN TX AND LA INTO MUCH OF AR...IN
   RESPONSE TO HEATING AND GLANCING INFLUENCE OF NM TROUGH.  MID LVL
   LAPSE RATES WILL BE COMPARATIVELY WEAK.  BUT COMBINATION OF RICH
   BOUNDARY LYR MOISTURE...MODERATE DEEP SHEAR AND BACKED LOW LVL FLOW
   WILL YIELD AN ENVIRONMENT FAVORABLE FOR CLUSTERS OF
   STORMS/SUPERCELLS THAT COULD PRODUCE TORNADOES AND LOCALLY DAMAGING
   WIND IN ADDITION TO VERY HEAVY RAIN.  THIS REGIME COULD PERSIST WELL
   INTO THE NIGHT AND SPREAD NNE ALONG CONFLUENT ERN PART OF BROADENING
   LLJ...EXTENDING SVR THREAT INTO PARTS OF MS AND WRN TN EARLY
   THURSDAY.
   
   ...MID MS VLY THIS AFTN/EVENING...
   SUBSTANTIAL DESTABILIZATION IS FORECAST OVER THE ERN MO/SRN IL/WRN
   KY AREA THIS AFTN...MORE THAN LIKELY AS ELEVATED MOISTURE ASSOCIATED
   WITH STRENGTHENING SSWLY LLJ IS MIXED TO THE SFC INVOF DEVELOPING
   WARM FRONT.  IF SUFFICIENT HEATING CAN OCCUR...SOMEWHAT UNCERTAIN
   GIVEN CURRENT SATELLITE IMAGERY...LOCALIZED CONVERGENCE MAY SUPPORT
   DEVELOPMENT OF SCTD SFC-BASED STORMS.  IF SFC-BASED DEVELOPMENT IS
   NOT REALIZED...ELEVATED ACTIVITY NOW DEVELOPING IN WRN/SRN MO COULD
   AFFECT REGION LATER TODAY AS STORMS BECOME ROOTED INCREASINGLY CLOSE
   TO THE SFC.  GIVEN 40+ KT DEEP WSW SHEAR...SOME OF THIS ACTIVITY
   COULD POSE A SVR THREAT LONG BEFORE PREVIOUSLY-DISCUSSED OVERNIGHT
   ACTIVITY.
   
   ..CORFIDI/GUYER.. 10/17/2007
   
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